I use one of these:
http://www.ebay.co.uk/itm/Dell-Power...item35b46281ad
You need to cut of the connector and link the blue wire to one of the black ones to switch it on and you're laughing.
There are 3 pairs of power wires in the cable, to I fitted 3 pairs of 4mm sockets so that I can attach my charger and soldering iron easily
18A for about 20 quid (including bits from Maplin or the like) Bargain
I can post up photos of the mods if you want?
Ian